By Chloe Fung Choi Yi

07 June 2016 - 16:01

'You can tweak your natural body clock through exposure to sunlight.' Photo (c) lensnmatter, licensed under CC BY 2.0 and adapted from the original.
'You can tweak your natural body clock through exposure to sunlight.' Photo ©

lensnmatter, licensed under CC BY 2.0 and adapted from the original.

Do you find it hard to wake up in the mornings? Chloe Fung Choi Yi, who won the FameLab science communication contest in Hong Kong, has some research-based tips that may help.

Why are some of us ‘morning people’, and some of us ‘night owls’?

When it comes to sleep habits, we often think of people as divided into two groups: the 'morning people' who leap out of bed easily in the mornings, and the late risers who press the snooze button in the mornings, but have more energy in the evenings.

But in reality, there are more than two categories - not simply just ‘early birds’ and ‘night owls’. Rather, we all fit somewhere along a spectrum.

When scientists classify different sleeping habits, they talk about chronotypes. This refers to our natural sleeping and waking pattern: our propensity to fall asleep at a certain time, and wake up at a certain time. It's the result of an interplay between genetics and lifestyle. Or more accurately, between the external 24-hour clock and our internal biological clock.

The internal clock is formed by a cluster of chemicals in the brain. These interact with each other, creating a regular chemical change, which produces the effect of an oscillating clock.

What's the difference between the external clock and our internal clock?

A day on earth lasts 24 hours. The sun dictates that duration, but our individual internal clocks do not necessarily agree. In fact, most of us are born with an internal 'day' that lasts longer than 24 hours. Some others have a shorter internal day, while others match the external clock exactly.

In response to the 24-hour light-dark cycle of the earth, those of us with longer internal days need to compress our natural cycles, making us later chronotypes. By contrast, people with shorter internal days must lengthen their natural cycle, resulting in earlier chronotypes. As most of us have internal clocks set longer than 24 hours, we tend to be late chronotypes, to different extents.

Do our internal clocks change throughout life?

Yes, this is also influenced by age. Young children are relatively early chronotypes, but grow to become later and later sleepers until a turning point at around the age of 20. From then on, we gradually sleep and wake earlier. It’s a matter of biology, not discipline. So, parents, stop trying to wake up your teenager when he sleeps in during the school holidays - he’s just obeying his genetics.

What proportion of the population are natural night owls or 'late chronotypes'?

First, let's explain how we work out a person's chronotype. The times that people usually fall asleep and wake up can vary, so we define chronotypes by the midpoint of a person’s sleep. For example, if someone falls asleep at midnight and wakes at 08.00, he or she would be a chronotype of 04.00.

The distribution of chronotypes follows a bell-curve that skews slightly to the right. According to Till Roenneberg, a professor of chronobiology at the University of Munich in Germany, more than four percent of people in Central Europe have the chronotype of 07.30 to 08.00, meaning they naturally want to fall asleep around 03.00 am or 03.30 am (assuming, for simplicity, that everyone sleeps eight hours). Quite a number of people would naturally fall asleep even later than that.

Are there any health benefits to waking up early and going to bed early? 

If we are forced to sleep and wake outside of our natural window of sleep, we become sleep-deprived. Late chronotypes, who must adjust their natural sleeping cycles according to social cues that favour waking early, are chronically sleep-deprived. There are zero health benefits to sleep deprivation. So in an ideal world, night owls would adjust their choice of jobs according to their natural body clocks.

Can you change your natural body clock so that you find it easier to wake up?

There are a number of zeitgebers - social or environmental cues that affect your biological clock - that we can turn to. An important one is light. The amount of light we expose ourselves to, and the timing of that exposure, can pull us back into sync with the external 24-hour clock.

If you have to drag yourself out of bed in the morning but feel peppier in the evenings, you can tweak your natural body clock through exposure to sunlight. For late chronotypes, the stronger the light they are exposed to during the day, and the less light at night, the earlier they can wake in the morning. Night owls who spend two or more hours outdoors each day can set their chronotypes a whole hour earlier. This means they will feel tired an hour earlier than usual in the evenings, and wake an hour earlier in the mornings.

However, for people who are naturally early risers, more sunlight exposure will have the opposite effect, making them wake later and feel sleepy earlier.

Other types of zeitgeber include the times we choose to eat breakfast, exercise, and interact with other people, as they determine the amount of time we expose ourselves to light and darkness.

How is indoor light different from natural light?

Artificial light is much dimmer than natural light. A well-lit room exposes our eyes to around 100 lux of light (the standard unit of light emittance), and even very bright artificial light is rarely more than a few hundred lux. Yet outside, even on a really rainy day, we are exposed to at least 10,000 lux; and under cloudless skies, we're exposed to 150,000 lux.

How does artificial light affect our natural body clocks?

We have light receptors at the back of our eyes. When light shines in, these receptors tell the brain how intense the light is, allowing our central command to synchronise our internal clock to the outside environment. Since artificial light is weaker than daylight, people working indoors are exposed to a much weaker cue for their sleep patterns. This either advances or delays their natural chronotypes.

Of course, the human sleep-wake cycle is a complex dance between many factors, not just light. But perhaps it would be better for our sleep cycles to have no artificial light at all. One study by the psychiatrist Thomas Wehr asked people to avoid exposure to artificial light altogether after sunset. The participants usually retired to their beds much earlier, sleeping for more than 12 hours, though almost always waking a few times in the night. They emerged from the experiment feeling more rested than they had ever felt before.

For those of us who are indoors most of the time, how can we fall asleep earlier and wake up earlier?

Serious advice? Get some more fresh air during daytime and spend less time watching a screen, especially after sundown. It will do you good, whether we’re referring to the quality of your sleep or the quality of your health.

People need sleep. It strengthens your immune system, allows your brain to consolidate memories and so much more. Some people are born with less need for sleep, but the rest of us need to listen to our bodies and give it enough time to rest and repair.

Chloe Fung Choi Yi is a biomedical science student at the University of Hong Kong. You can watch her compete in the international FameLab finals on 8-9 June 2016. 

Watch Chloe's winning presentation on the science of sleep.

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